Feeding and feeding-related behavior will be investigated in relation to a systematic study of receptor sensitivity to determine whether this behavior can be regulated by efferent receptor control. Using single unit recording or receptor responses to constant chemical (feeding) stimuli, receptor change will be monitored in relation to: 1) post-prandial behavior; 2) food-searching behavior, 3) exploratory behavior; 4) locomotory behavior; 5) circular, excitational behavioral. These behaviors can be measured in the fly by simple geometric techniques either directly or from video tape records. By recording receptor sensitivity and these behavioral modes in the same animal, through a technique of reversible, whole-animal single unit recording and measurement of behavioral display, receptor changes can be evaluated as a behavioral control process. One means by which behavioral regulation through excitational receptor states could occur would be by efferent regulation of receptor gain. Investigation will include behavioral correlations and a study of efferent regulatory mechanisms involving hormonal, neural and ingestional feedback. That is, receptor changes will be measured in situations where the behavior is known and postingestional events which influence behavior (crop-emptying, etc) will be manipulated and receptor changes monitored. The time course and nature of such changes will be examined. Additionally, locomotory behaviors will be observed directly together with a monitor of receptor changes in the same animals.